Sound recording and reproducing apparatus



July 28, 1953 A. c. DAvls SOUND RECORDING AND REPRDDUCING APPARATUSFiled sept. 12, 1949 2 Sheets-Sheet 1 ATTORNEY.

`Iuly 28, 1953 A. c. DAvls 2,646,989

SOUND RECORDING AND REPRODUCING APPARATUS Filed Sept. 12, 1949 2Sheets-Sheet 2 lllll'mllh W y E QTHUQ C1 .DAV/.5,

ATTORNEY.

Patented July 28, 1953 UNITED STATES 'PATENT AOFFICE SOUND RECORDING ANDREPRODUCING APPARATUS- Arthur C. Davis, Burbank, Calif.

Application September 12, 1949,.SerialNo. 115297 4:01am. l

This invention relates to improvements 4in sound recording andreproducing equipment and is particuiarly directed rto improvedVrneansior handling` sound recordings magnetically recorded upon acontinuous tape. The tape may be cellulosic and provided with amagnetizable deposit or coating or the tape may be of any vothersuitable material capable of receiving and carrying a reproduciblerecord of audible sounds of various types.

Although magnetic recordings upon 'filamentary carriers have beenavailable for many years, adequate synchronized equipment foreilectively handling such tape has not beeninade available. The presentinvention is particularly directed to apparatus which may be used forrecording or reproducing magnetic recordings from filamentary tapes, theapparatus being arranged so as to permit the tape to 'oe driven at auniform, consta-nt speed without the introduction of variations,lutters, and other deviations which impair the quality andcharacteristics Vof the sound `being either reproduced or recorded.

The invention, moreover, pertains to a construction Which permitsrecording and/or reproduction to be carried out in the same piece ofequipment without interference due to the proX- imity of amplifiers,oscillators or other electrical units which may be Vemployed in therecording or Vreproduction and ampliiication of sound. As a result, thedevices of the present invention may be embodied in a complete,com-pact, and portable sound recording or reproducing unit and it is notnecessary to isolate the recording `head or heads from the rest of theequipment.

Furthermore. the invention describes `means and meth-ais cf mounting thedriving means in such manner that positive, uniform speed is'imparted toa nlm provided with sprocket holes and employingdriving sprocketsWithout the generation or" sidebands, vibrations, or flutter which mayimpair the quality of the recordings.` The present invention utilizesresistance of the lm to variable flexure as a primary damping means andeliminates the use of dashpots.

The above and Various other objects and `advantages of the presentinvention will become apparent to those skilled in the art from thefollowing description of exemplary forms embodying the construction. Inorder to facilitate understandi ing reference will be had to theappended drawings in which:

Fig. 1 is a front view of -a portion fof a film recording andreproducing device, the cover lof the housing being illustratedin openposition.

Fig. 2 is a side elevation, partly insectionjillustrating the recordingand reproducing head and the motor drive.

3 is a rear View taken along the plane 'III-III of Fig. 2 showing thearrangement Yof stabilizing means.

Fig. fi is a transverse ysection taken alongthe plane IV-TV in Fig. 1 onan enlarged 'scaleillustrating a preferred driving connection.

Fig. 5 is an enlarged partial section o'f .an adjustment means, saidsection being 'taken along the plane V-V in Fig. l.

Figsyand '.7 vare transverse vsections taken along planes VI--VI andVII-VII in Fig. 4, illustrating in greater detail portions of thedriving connections.

As best shown in Figs. `1 `'and '2, lthe recorder is provided with a'freely-journaled, smoothspac'ed, Weighted recording and reproducing.drum lil arranged to Yirictionally receive strip ilm over the majorportion of its periphery. The drum IIJ may be Acarried 'by a shaft SH,journaledin a suitable `bearing l2 carried by thepanel I3 .of thereproducing unit. The shaft may be provided with aheavy flywheel i4.

:in actual practice the strip lm 9 l(or other A"iilamen'tary carrier) iscarried upon la suitable ing ,roller l? `then .over the surface of the.drum

.i .0 ,past .another .stabilizing roller .lil into Acontact with .thedriven `sprocket L6 and Vout .by .Way of the guiding roller iii.Suitable selectivelyoper- .able pressure rclleiuassemblies 4.9 .and IBnor- .mallykeep .thelm in positive engagement with the sprocket EB.

The drum iii is positioned within a pickupand .recording ease 1-29Vc:instituting a magnetic shield vand .made of metals which .adequatelyandfcom- .pletely lshield the pickup .and reproducing heads. Preferably.the .pickup case is made rof laminated construction, .for example, alayer .of copper Aand .two .layers of .MU metal. .The case 20 .may .be.provided with side Walls, top vand bottom `Walls 4(the .bottom beingported so .as .to permit entry and withdrawal `of the lm 9.) and abacklwall `2l. .The front of .the case may be open and. capable ,of .being.electively closed bymeans v.of la hinged .door 22. The entire case imay Mbe grounded.

Positioned within the case surrounding the drum I is a head mountingplate 23. The head mounting plate 23 carries a recording head indicatedat 25, an erasure head 26, and a pickup or reproducing head 21. The headmountingr plate 23 may be U-shaped so as to straddle the shaft I| of thedrum and is supported from the back wall 2| of the pickup case byadjustable means whereby the distance of the plate from the back Wallmay be varied so as to place the various heads -21 along one margin orthe other of the lm 9 or at any intervening position. It is to beunderstood that since the magnetic recording itself may be quite narrowa number of longitudinally extending parallel recordings may be carriedby a single strip of film.

The adjustably positionable means for holding the plate in a selectedplane transverse to the axis of the drum I0 is well illustrated in Fig.5. As there shown, the plate 23 carries a hollow stud in threadedengagement with an internally threaded port in the plate 23, the base ofsuch stud resting against the bottom or back wall 2| of the pickup case.Extending through the hollow stud 30 is a fastening screw 3| in threadedengagement with the bottom of the case 2| and the supporting panel I3.It will be evident that by loosening the fastening screw 3| the stud 30may be rotated so as to move the entire head mounting plate 23 into adesired plane, since the rest of the hollow stud is several times thethickness of the plate 23.

Details as to construction of the various heads 25-21 are not necessaryhere but attention may be drawn to the fact that each of the heads isprovided with its own base plate such as 25 having slots in each andfastening screws 28 extending through said slots into the mounting plate23. In this manner each of the heads 25--21 may be moved toward or awayfrom` the surface of the drum I0.

It is also to be noted that a small idler roller such as 29 is carriedby the head mounting plate 23 between the heads 25 and 26 and the lm 9may be caused to pass over this roller or selectively be carried by thesurface of the drum I0 beneath such roller. If, therefore, the device isnot being used for recording purposes, the film 9 need not pass overroller 29 (such passage bringing the film into operative contact withthe recording head 25 and the erasing head 26) but instead may contactsubstantially the entire surface of drum I6 until it leaves such surfaceand passes over idler roller 29' at which point the film is brought intooperative proximity with the pickup head 21. up head 21 then the filmcan pass beneath roller 29 and maintain its contact with the surface ofthe drum I6.

Particular attention is drawn to the stabilizing rollers I1 land I1which are in yielding contact with the outer surfaces of the filmextending between the driven sprocket I6 and the drum III. It will benoted that these stabilizing rollers are carried upon stub shafts 33extending through horizontally disposed slots 34 in the supportingpanel. Each stub shaft 33 is carried by the upper `end of a bell cranklever 34. Each bell crank is provided with a long larm and a short arm,the short arm being indicated at 35. The stub shafts 33 are mounted atthe end of the longer arm. Each bell crank lever 34 is pivotallysupported upon a stud 36, the studs 36 and 36' being located on oppositesides of a center line connecting shaft l I with the drive shaft 46 ofthe sprocket I6. It may also be noted that these points When it is notdesired to use the'pickof pivotal connection 36 and 36 are spaced adistance materially less than the diameter of drum IU, such distanceapproximating the diameter of the driving sprocket I5.

The outwardly directed short arms of the bell crank levers Iare eachconnected by means of a spring 31 to an .adjustment rod 38 carried by abracket 39 fastened to the back of the panel. The two springs andadjustment rods are preferably in substantially parallel relation andare parallel to the center line joining shaft I of the drum I0 with thedriving shaft 46 of sprocket I6.

It will be noted that this arrangement places the stabilizing rollers I1and I1' in close proximity to the surface of the drum IU and themovement of the stabilizing rollers is in ya plane substantially tangentto the surface of the drum I9 and between such drum and the drivingsprocket I6. It has been found that this arrangement is extremelyeicient in maintaining proper contact with the drum I0 and ineliminating the formation of loops and in absorbing flutter or othervariations in linear speed of the film 9.

rIhe shaft 46 of the driving sprocket I6 is suitably journaled as in abearing 42 carried by the panel I3. This shaft is connected to acupshaped element 43 carried by a torque shaft 44, in alignment withshaft 46, by means of a transversely extending strip of resilient metal45 (see Figs. 4 and 6). The strip of metal 45 is preferably flat, liesin a plane transverse to the shaft 46 and is connected to the shaft 46at its center and to the edges of the cup-shaped member 43. It should becapable of a certain amount of exure in the event torque shaft 44 movestoward or away from drive shaft 46. The other end of the torque shaft 45is provided with a similar but larger cup-shaped member 41 which isconnected to a hollow quill 56. The adjacent end of quill carries anoutwardly flanged coupling 5|, the margins of such coupling beingconnected to the outer margins of the element 41 by means of a prongedresilient connector having arms 48 and a center ring 49. The ends of thearms 48 are connected to the cup 41 whereas the ring 49 is connected to5|. The connector arms transmit rotation from the quill to the torqueshaft 44 while absorbing and damping vibration.

The quill 50 is journaled in a gear case 52 and may be provided with aworm gear 53 in operative engagement with a worm 54 carried by the shaftof a motor 55 suspended from shock absorbing mounts 56 carried by asuitable bracket or other support 51.

The present arrangement does not employ a dashpot or other resistiveelement for damping, as in the case of several prior tightloop filmtransporting mechanisms. It will also be noted that, in the instantarrangement, the upper ends of springs 31 are fastened to the frame andthis results in a non-linear compliance of the springs, permitting themto act as soft limiters to large amplitude variations of the arms 34upon which rollers I1 are mounted. Primary damping in the instant systemis attained by utilizing the resistance of film to iiexure; as therollers I1 approach. or recede from each other, the amount of filmwrapped around drum I0 and each of rollers I1 is appreciably changed.The present arrangement therefore uses the resistance to variableiiexure of the film as damping and the compliances are operated asnon-linear elements limiting large amplitude oscillations, thus givingthe effect of additional damping in reaching stable operatingconditions.

Although a specific example has been described in detail so that thoseskilled in the art may readily appreciate the advantages and attain thesame, various changes and adaptations are contemplated and will readilyoccur to skilled technicians, and all changes and modificationsutilizing the teachings of this invention and coming within the scope ofthe appended claims are embraced thereby.

I claim:

1. In a sound recording and reproducing apparatus: a freely-journaled,smooth-surfaced, weighted recording and reproducing drum, arranged tofrictionally receive strip film over the major portion of its periphery;a shielded pickup case surrounding said drum, and including a headmounting plate in a plane transverse to the axis of the drum; means foradjustably positioning said mounting plate in a selected planetransverse to the drum axis; a magnetic head carried by the plate withits face out of operative range of lm on said drum; an idler rollerjournaled in proximity to said drum and head, said roller beingpositioned to divert lm from and return the lm to said head whereby thelm so diverted by the roller passes in operative relation to the head.

2. In a sound recording and reproducing apparatus: a freely journaled,smooth surfaced, weighted, recording and reproducing drum arranged tofrictionally receive strip lm over the major portion of its periphery; adriving sprocket extending between the sprocket and drum; separatespring means for yieldably urging each of said rollers toward the otherand means restricting motion of said rollers to a path virtuallytransverse to a line connecting the axes of the drum and sprocket and inclose proximity to the drum to vary the amount of strip film in contactwith the drum; a shielded pickup case surrounding said drum andincluding a head mounting plate in a plane transverse to the axis of thedrum, and means for adjustably positioning said mounting plate in aselected plane transverse to the drum axis.

4. In a sound recording and reproducing apparatus: a freely-journaled,smooth-surfaced Weighted recording and reproducing drum, arranged tofrictionally receive strip nlm over the major portion of its periphery;a driving sprocket mounted upon a shaft parallel to the axis of the drumand spaced therefrom, said sprocket being arranged to engage strip iilmpassing thereover on the way to and returning from said drum;

` adjustable means for releasably holding nlm in mounted upon a shaftparallel to the axis of the drum and spaced therefrom, said sprocketbeing arranged to engage strip lm passing thereover on the way to andreturning from said drum; a pair of stabilizing rollers, each inyielding contact with the outer surface of a lay of film extendingbetween the sprocket and drum; means for yieldably urging said rollerstoward each other and means restricting motion of said rollers to a pathvirtually transverse to a line connecting the axes of the drum andsprocket and in close proximity to the drum; a shielded pickup casesurrounding said drum and including a head mounting plate in a planetransverse to the axis of the drum and means for adjustably positioningsaid mounting plate in a selected plane transverse to the drum axis; amagnetic head carried by the plate with its face out of operative rangeof nlm on said drum; and an idler roller journaled in proximity f tosaid drum and head, said roller being positioned to divert nlm from andreturn the lm to said head, whereby the film so diverted by the rollerpasses in operative relation to the head.

3. In a sound recording and reproducing apparatus: a freely-journaled,smooth-surfaced, weighted recording and reproducing drum, arranged tofrictionally receive strip lm over the major portion of its periphery; adriving sprocket mounted upon a shaft parallel to the axis of the drumand spaced therefrom, said sprocket being arranged to engage strip nlmpassing thereover on the way to and returning from said drum; adjustablemeans for releasably holding lm in engagement with the sprocket; a pairof stabilizing rollers movably positioned between the drum and sprocket,each stabilizing roller being in yielding f contact with the outersurface of a lay of lm engagement with the sprocket; a pair ofstabilizing rollers movably positioned between the drum and sprocket,each stabilizing roller being in yielding contact with the outer surfaceof a lay of film extending between the sprocket and drum; separatespring means for yieldably urging each of said rollers toward the otherand means restricting motion of said rollers to a path virtuallytransverse to a line connecting the axes of the drum and sprocket and inclose proximity to the drum to vary the amount of strip lm in contactwith the drum; a shielded pickup case surrounding said drum andincluding a head mounting plate in a plane transverse to the axis of thedrum, and means for adjustably positioning said mounting plate in aselected plane transverse to the drum axis; a magnetic head carried bythe plate with its face out of operative range of film on said drum; andan idler roller journaled in proximity to said drum and head, saidroller being positioned to divert film from and return the film to saidhead whereby the iilm so diverted by the roller passes in operativerelation to the head.

ARTHUR CHAS. DAVIS.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 680,315 Collins Aug. 13, 1901 766,261 Jebsen Aug. 2, 19041,777,682 Sponable Oct. 7, 1930 1,996,732 Whitman Apr. 2, 1935 2,251,322Buhrnedorf Aug. 5, 1941 2,266,755 Herzig Dec, 23, 1941 2,273,391Yerkovich Feb. 17, 1942 2,408,320 Kuhlik Sept. 24, 1946 2,430,449 BrownNov. 11, 1947 2,463,411 Mynard Mar. 1, 1949 2,518,556 Kalb et al Aug.15, 1950 FOREIGN PATENTS Number Country Date 650,072 Germany Sept. 16,1937 64,146 Norway Nov. 10, 1941

